Change in knee angle influences the rate of medial tibial cartilage volume loss in knee osteoarthritis.

OBJECTIVES: Identifying factors that influence the rate of cartilage loss at the knee may help to prevent or delay the progression of knee osteoarthritis (OA). Changes in knee alignment alter knee joint load and may affect the rate of cartilage loss. The aim of this study was to determine whether change in knee alignment between baseline and 2 years is associated with a change in knee cartilage volume in knee OA in the subsequent 2.5 years.

METHODS: Seventy-eight adults with symptomatic knee OA were recruited using a combined strategy. Radiographs were performed at time 0 and 2 years to determine change in knee alignment, measured on a continuous scale. Magnetic Resonance Imaging was performed at 2 and 4.5 years to determine annual percentage change in medial and lateral tibial cartilage volumes.

RESULTS: In multivariate analyses, for every 1 degrees change toward genu valgum, there is an associated 0.44% reduction in the rate of annual medial tibial cartilage volume loss (95% CI: -0.85%, -0.04%, P=0.03). Similarly, because our measures of change in alignment and cartilage volume were continuous, these results also implied that for every 1 degrees change toward genu varum, there was an associated 0.44% increase in the rate of annual medial tibial cartilage volume loss. Change in knee angle did not significantly affect the rate of loss of the lateral tibial cartilage volume (P=0.95).

CONCLUSION: Our results have demonstrated that progressive change toward genu valgum reduced the annual rate of medial tibial cartilage volume loss in people with knee OA, without expediting the rate of lateral tibial cartilage volume loss. These findings suggest that methods to reduce varus alignment may delay the progression of medial tibiofemoral OA and warrant further investigation.